Recovery of tungsten from acidic solutions rich in calcium and iron

Abstract During the decomposition of low-grade scheelite ore using HCl-H3PO4 solution, a large amount of Ca and Fe in the ore are released into the leach liquor, which complicates subsequent purification. Due to the difficulties of separation, a novel solvent extraction process was developed for extracting tungsten from acidic solutions rich in calcium and iron. The impacts of calcium and iron impurities on the extraction were investigated, and the results showed that co-extraction of calcium led to the loss of tungsten. Therefore, pre-decalcification was carried out by adding H2SO4 to the acidic leach liquor before extraction, and a high-quality gypsum product with a low tungsten content (